Mr. Jeffreys un British Mullusca. 109 



Lukis found a specimen of tliis curious shell at Herm many years 

 ago, and obligingly presented me witii it. It bears a suspicious re- 

 semblance to the Rissoa crassicosta of the late Professor C. B. Adams, 

 which is described in his ' Synopsis Conchyliorum Jamaicensium,' 

 &c., p. 6 ; but my specimen, as well as Montagu's description, shows 

 no trace of the numerous and very fine transverse strise which cross 

 the ribs in the West Indian shell. My shell has not the columellar 

 tubercles noticed by iNIontagu ; and his description may have been 

 taken from a broken specimen, in which the sutural extremities of 

 the ribs were left on the pillar lip, so as to give the appearance of 

 tubercles. 



R. unica. Aclis unica, iii. 222. I had overlooked Mr. Clark's 

 excellent paper on the animal, which was published in the 'Annals 

 of Natural History' for 1854, p. 122, and in which he clearly made 

 it out to be a Rissoa. I am also satisfied, on conchological grounds, 

 that it ought to be placed in that genus, and not in Aclis or Chem- 

 nitzia. 



Barleeia rubra (Clark). Rissoa rubra, iii. 120. Bantry {Rev. 

 Mr. Norman) ; var. alba, pellucida. Serk, on Codium tomentosum. 

 This may be the variety noticed by Montagu (Test. Brit. ii. 321). 

 The bright-red colour of the operculum (with its peculiar sj)ike, like 

 that of a Keritiiui) contrasts singularly with that of the shell. 



Jeffreysia diaphana, iii. 152. Falmouth; Penzance; Cumbrae ; 

 Bantry \Rei\ Mr. Norinan). In its stomach Mrs. CoUings detected 

 a species of Lithocystis, allied to L. Allmanni. 



J. opalina, iii. 154. Cumbrae {Rev. Mr. Norman). 



5.1 Gulsonae. Odostomia Gulsonce, iv. 281 ; var. minor. I found 

 a specimen of this variety at Guernsey, which was not larger than 

 the Odostomia minima. 



Caecum glabrum, iii. 181. Clyde district {Rev. Mr. Norman). 

 The curious form and structure of the operculum suggest the aflinity 

 of this genus to Bifrontia. 



Euomphalus nitidissimus. Skeneal nitidissima, iii. 158. I will 

 now, without preface, introduce this anomalous and strange-looking 

 creature by the representation given in PI. III. fig. \b a,b, and 16 a-c. 

 While I was at Serk last autumn, I had the good fortune to observe, 

 with the aid of an excellent microscope, for several hours, the form 

 and motions of the animal, — comparing with it, at the same time, 

 Skenea planorbis, an animal supposed to be its congener, but which 

 is, in fact, totally dissimilar in respect of the soft parts as well as of 

 the shell. Both are abundant almost every where on our rocky coasts, 

 especially on the Codium tomentosum, which appears to constitute 

 the food of these and other phytophagous mollusks ; and it is strange 

 that the animal of the Euomphalus nitidissimus has so long escaped 

 observation. The following is a description of it, as taken on the 

 spot : — 



Animal flaky-white, nearly hyaline ; it has no vestige of any ten- 

 tacles, but instead of them it is provided with a large broad veil, 

 which is bilobed in front, and has its outer margin fringed with short 

 and close-set but irregularly disposed cilia. Some of these cilia are 



